Quadrotor offboard servo control


I am studying a quadrotor’s response to a payload drop using a servo. I am using an ODroid (running Ubuntu 16.04) to run a control algorithm and generate a reference trajectory for the drone to follow. I know I can operate the servo by setting one of the aux1 passthroughs to a switch on my RC in QGroundControl. I am using the 3DR DIY Quad airframe.

I want to send a command from the ODroid to the Pixhawk to flip the servo at a specific time. This way the payload is dropped at the same time in every experiment. Should I try to send a mavlink message containing the command to operate the servo? Edit the mixer file and send a control input to flaps/spoiler/brake? Any help or insight into how servos work on PX4 would be appreciated.

have you got it working? I am interested in how you controlled the servo in offboard.